The invention relates to an oscillator in a liquid comprising an actuator element oscillating in a reciprocating manner, whereby the distance between the ends of the actuator element varies, and a sound-producing element attached to the actuator element, whereby the actuator element generates a motion in the sound-producing element for producing a sound, the oscillator being provided open, whereby liquid pressure acts both on a first surface and on a second surface of the wall of the sound-producing element while the oscillator is in the liquid.
A typical underwater sound source includes an actuator oscillating in a reciprocating manner such that the distance between the actuator ends varies. At the actuator ends there is attached a sound-producing element, whereby the actuator, while oscillating in a reciprocating manner, generates a motion in the sound-producing element such that a sound will be produced. Underwater sound sources of this kind are disclosed, for instance, in publications U.S. Pat. No. 5,016,228, U.S. Pat. No. 5,497,357 and U.S. Pat. No. 6,076,629. Typically the sound sources are encapsulated such that water is not able to penetrate inside the sound-producing element. The tightness of the sound source encapsulation is thus subjected to high standards. Pressure compensation in the interior of the sound source may require complicated equipment. Further, to make the encapsulated structure sufficiently sturdy to resist external impacts, for instance produced by an explosion, is extremely challenging, and therefore the encapsulated solution is quite expensive to manufacture. There are also known sound sources having an open structure, in which the pressure of water will be able to act on both sides of the sound-producing element. However, at low frequencies the efficiency of these solutions to produce sound is not sufficient for most uses.